DIN 18599: Complete Guide to Energy Performance Calculation for Buildings

DIN 18599 is the comprehensive German standard for calculating the energy performance of buildings, providing detailed methodologies for determining net, final, and primary energy demand across all building energy systems. This standard is fundamental to German building energy regulations (EnEV/GEG) and represents one of the most sophisticated building energy calculation frameworks in Europe. Understanding DIN 18599 is essential for building designers, energy consultants, and HVAC engineers working in the German market or seeking to apply advanced energy performance calculation methods.

The standard addresses the complete energy balance of buildings, covering heating, cooling, ventilation, lighting, domestic hot water, and auxiliary energy consumption. It provides both detailed calculation procedures and simplified methods, enabling accurate energy performance assessment from early design stages through detailed analysis. This comprehensive guide covers all 13 parts of DIN 18599, calculation methodologies, key formulas, reference tables, and practical application examples.

Introduction to DIN 18599

Purpose and Scope

DIN 18599 establishes standardized procedures for calculating the energy performance of buildings, serving multiple critical purposes:

Regulatory Compliance:

Basis for compliance with German Energy Saving Ordinance (EnEV)
Foundation for Building Energy Act (GEG) requirements
Energy Performance Certificate (EPC) generation
Building permit documentation

Design Optimization:

Early-stage energy performance assessment
Comparison of design alternatives
Identification of energy efficiency measures
Cost-benefit analysis of energy systems

Performance Verification:

Verification of design performance
Post-construction energy assessment
Building energy rating and classification
Benchmarking against standards

Energy Management:

Operational energy monitoring
Energy efficiency improvement planning
Retrofit analysis and prioritization
Life-cycle energy assessment

Structure of DIN 18599

DIN 18599 is organized into 13 parts, each addressing specific aspects of building energy performance:

Part 1: General Balancing Procedures, Terms and Definitions, Zoning, and Evaluation of Energy Sources

Fundamental calculation procedures
Terminology and definitions
Building zoning methodology
Energy carrier evaluation
Primary energy factors

Part 2: Net Energy Demand for Heating and Cooling of Building Zones

Zone-based heating demand calculation
Zone-based cooling demand calculation
Internal heat gains
Solar heat gains
Thermal building characteristics

Part 3: Net Energy Demand for Air Conditioning

Air conditioning system energy demand
Sensible and latent cooling loads
Dehumidification requirements
Humidification requirements

Part 4: Net and Final Energy Demand for Lighting

Daylight availability
Artificial lighting requirements
Lighting system efficiency
Control system impact

Part 5: Final Energy Demand of Heating Systems

Boiler efficiency
Heat pump performance
District heating systems
Electric heating systems
System losses and auxiliary energy

Part 6: Final Energy Demand of Ventilation Systems

Mechanical ventilation energy
Heat recovery efficiency
Fan power requirements
Control system impact

Part 7: Final Energy Demand of Air Conditioning Systems

Cooling system efficiency
Chiller performance
Heat rejection systems
Auxiliary energy consumption

Part 8: Net and Final Energy Demand of Domestic Hot Water Systems

Hot water demand profiles
System efficiency
Distribution losses
Storage losses

Part 9: Final and Primary Energy Demand of Power Generating Plants

Combined heat and power (CHP)
Photovoltaic systems
Wind energy systems
Energy storage systems

Part 10: Boundary Conditions of Use, Climatic Data

Climate zones and reference years
Indoor design conditions
Usage profiles
Operating schedules

Part 11: Building Automation

Control system efficiency
Building management systems
Demand-based control
Optimization strategies

Part 12: Tabulation Method for Residential Buildings

Simplified calculation method
Tabulated values
Quick assessment procedures
Residential building applications

Part 13: Energy Performance of Buildings – Calculation of Energy Needs for Heating and Cooling, Internal Temperatures, and Sensible and Latent Heat Loads

Detailed load calculations
Internal temperature determination
Sensible heat load analysis
Latent heat load analysis

Key Energy Terms and Definitions

Understanding DIN 18599 requires precise definition of energy terms:

**Net Energy Demand ( $Q_{N}$ ):** The energy required at the system boundary to maintain specified indoor conditions, excluding system losses:

Q_{N} = Q_{H,N} + Q_{C,N} + Q_{V,N} + Q_{L,N} + Q_{W,N}

Where:

$Q_{H,N}$ = Net heating energy demand
$Q_{C,N}$ = Net cooling energy demand
$Q_{V,N}$ = Net ventilation energy demand
$Q_{L,N}$ = Net lighting energy demand
$Q_{W,N}$ = Net domestic hot water energy demand

**Final Energy Demand ( $Q_{F}$ ):** The energy delivered to the building, including system losses:

Q_{F} = Q_{N} + Q_{loss} + Q_{aux}

Where:

$Q_{loss}$ = System distribution and storage losses
$Q_{aux}$ = Auxiliary energy (pumps, fans, controls)

**Primary Energy Demand ( $Q_{P}$ ):** The total energy required from primary energy sources:

Q_{P} = \sum_{i} (Q_{F,i} \times f_{P,i})

Where:

$Q_{F,i}$ = Final energy demand for energy carrier $i$
$f_{P,i}$ = Primary energy factor for energy carrier $i$

**Primary Energy Factors ( $f_{P}$ ):**

Primary energy factors convert final energy to primary energy, accounting for extraction, conversion, and distribution losses:

Energy Carrier	Primary Energy Factor ( $f_{P}$ )	Notes
Natural gas	1.1	Standard value
Heating oil	1.1	Standard value
District heating (fossil)	1.3	Varies by source
District heating (renewable)	0.0	Renewable sources
Electricity (grid)	1.8	German grid mix (2021)
Electricity (renewable)	0.0	Direct renewable supply
Biomass	0.2	Sustainable biomass
Heat pump (air source)	0.6-1.0	Depends on COP and electricity mix
Heat pump (ground source)	0.4-0.8	Depends on COP and electricity mix
Solar thermal	0.0	Renewable source
Photovoltaic	0.0	Renewable source

Energy Performance Indicator (EPI):

EPI = \frac{Q_{P}}{A_{NGF}}

Where $A_{NGF}$ = Net floor area (Nettogrundfläche) in m²

Annual Energy Performance:

Q_{P,annual} = Q_{P,H} + Q_{P,C} + Q_{P,V} + Q_{P,L} + Q_{P,W} - Q_{P,gen}

Where $Q_{P,gen}$ = Primary energy from on-site generation

Part 1: General Balancing Procedures

Building Zoning

DIN 18599 requires buildings to be divided into thermal zones based on:

Zone Criteria:

Thermal characteristics (heated/unheated)
Usage type (residential, office, commercial)
Operating schedules
Internal heat gains
Temperature requirements

Zone Types:

Zone Type	Description	Typical Use
Heated zone	Maintained at design temperature	Living spaces, offices
Unheated zone	No heating, but enclosed	Garages, storage
Conditioned zone	Heating and cooling	Offices, retail
Buffer zone	Adjacent to heated zones	Stairwells, corridors

Zone Boundary Definition:

External boundaries: Building envelope
Internal boundaries: Between zones with different conditions
Ground boundaries: Contact with ground or unheated spaces

Energy Balance Methodology

Monthly Balance Method: DIN 18599 uses monthly balance calculations for annual energy assessment:

Q_{N,month} = Q_{H,N,month} + Q_{C,N,month} + Q_{V,N,month} + Q_{L,N,month} + Q_{W,N,month}

Annual Summation:

Q_{N,annual} = \sum_{i=1}^{12} Q_{N,month,i}

System Boundary: The calculation boundary includes:

Building envelope
All energy systems
Distribution systems
Storage systems
Control systems

Energy Carrier Evaluation

Energy Carrier Classification:

Category	Energy Carriers	Primary Energy Factor Range
Fossil fuels	Natural gas, heating oil, coal	1.1-1.3
Electricity	Grid electricity	1.8
District energy	District heating/cooling	0.0-1.3
Renewable	Solar, biomass, geothermal	0.0-0.2
Waste heat	Industrial waste heat	0.0-0.5

Time-Dependent Primary Energy Factors: For electricity, primary energy factors may vary by time:

f_{P,el}(t) = f_{P,base} + \Delta f_{P}(t)

Where $\Delta f_{P}(t)$ accounts for grid mix variations.

Part 2: Net Energy Demand for Heating and Cooling

Heating Energy Demand

Basic Heating Balance:

Q_{H,N} = Q_{H,trans} + Q_{H,vent} - Q_{H,int} - Q_{H,sol}

Where:

$Q_{H,trans}$ = Transmission heat losses
$Q_{H,vent}$ = Ventilation heat losses
$Q_{H,int}$ = Internal heat gains
$Q_{H,sol}$ = Solar heat gains

Transmission Heat Losses:

Q_{H,trans} = \sum_{i} (U_{i} \times A_{i} \times F_{x,i}) \times (\theta_{int} - \theta_{e}) \times t

Where:

$U_{i}$ = Thermal transmittance of element $i$ (W/m²·K)
$A_{i}$ = Area of element $i$ (m²)
$F_{x,i}$ = Temperature correction factor for element $i$
$\theta_{int}$ = Internal temperature (°C)
$\theta_{e}$ = External temperature (°C)
$t$ = Time period (hours)

Temperature Correction Factors:

Building Element	$F_{x}$	Description
External wall	1.0	Direct exposure
Roof	1.0	Direct exposure
Ground floor	0.5-0.7	Ground contact
Wall to unheated space	0.5-0.8	Adjacent unheated zone
Wall to ground	0.3-0.5	Below-grade contact

Ventilation Heat Losses:

Q_{H,vent} = 0.34 \times V_{air} \times (\theta_{int} - \theta_{e}) \times t

Where:

$V_{air}$ = Air volume flow rate (m³/h)
0.34 = Volumetric heat capacity of air (Wh/m³·K)

Air Volume Flow Rate:

V_{air} = n \times V_{room}

Where:

$n$ = Air change rate (1/h)
$V_{room}$ = Room volume (m³)

Air Change Rates:

Building Type	Air Change Rate $n$ (1/h)	Notes
Residential (natural ventilation)	0.3-0.5	Minimum ventilation
Residential (mechanical)	0.3-0.6	Controlled ventilation
Office (natural)	0.5-1.0	Window ventilation
Office (mechanical)	1.0-2.0	Full mechanical
Retail	1.0-3.0	High occupancy
Schools	2.0-4.0	High fresh air requirement

Internal Heat Gains:

Q_{H,int} = Q_{int,persons} + Q_{int,equipment} + Q_{int,lighting}

Internal Heat Gain Values:

Source	Heat Gain (W/m²)	Notes
Persons (residential)	2-4	Average occupancy
Persons (office)	4-8	Office occupancy
Equipment (residential)	2-4	Household appliances
Equipment (office)	8-15	IT equipment, office machines
Lighting (residential)	1-3	Standard lighting
Lighting (office)	3-8	Office lighting

Solar Heat Gains:

Q_{H,sol} = \sum_{i} (g_{i} \times A_{window,i} \times I_{sol,i} \times F_{shade,i}) \times F_{frame,i}

Where:

$g_{i}$ = Total solar energy transmittance (g-value) of window $i$
$A_{window,i}$ = Window area (m²)
$I_{sol,i}$ = Incident solar radiation (kWh/m²)
$F_{shade,i}$ = Shading reduction factor
$F_{frame,i}$ = Frame area reduction factor

G-Values (Total Solar Energy Transmittance):

Glazing Type	G-Value	SHGC Equivalent
Single pane clear	0.85	0.85
Double pane clear	0.75	0.75
Double pane Low-E	0.50-0.65	0.50-0.65
Triple pane Low-E	0.40-0.55	0.40-0.55
Solar control glazing	0.20-0.40	0.20-0.40

Shading Reduction Factors:

Shading Type	$F_{shade}$	Notes
No shading	1.0	Full solar gain
External blinds (closed)	0.1-0.3	Effective shading
Internal blinds (closed)	0.3-0.5	Less effective
Overhang (south)	0.6-0.8	Seasonal variation
Trees/vegetation	0.4-0.7	Depends on density

Monthly Solar Radiation (kWh/m²):

Orientation	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
South (vertical)	60	80	100	90	70	60	65	80	100	90	60	50
East/West (vertical)	30	45	60	70	80	75	80	75	60	45	30	25
North (vertical)	15	25	35	40	45	50	50	45	35	25	15	10
Horizontal	25	45	80	120	140	150	145	120	85	50	30	20

Note: Values are approximate for Central European climate, actual values depend on location and climate zone.

Cooling Energy Demand

Basic Cooling Balance:

Q_{C,N} = Q_{C,trans} + Q_{C,vent} + Q_{C,int} + Q_{C,sol} - Q_{C,storage}

Where:

$Q_{C,trans}$ = Transmission heat gains
$Q_{C,vent}$ = Ventilation heat gains
$Q_{C,int}$ = Internal heat gains
$Q_{C,sol}$ = Solar heat gains
$Q_{C,storage}$ = Thermal storage effect

Transmission Heat Gains:

Q_{C,trans} = \sum_{i} (U_{i} \times A_{i}) \times (\theta_{e} - \theta_{int}) \times t

Ventilation Heat Gains:

Q_{C,vent} = 0.34 \times V_{air} \times (\theta_{e} - \theta_{int}) \times t

Internal Heat Gains (Cooling): Same sources as heating, but all contribute to cooling load:

Q_{C,int} = Q_{int,persons} + Q_{int,equipment} + Q_{int,lighting}

Solar Heat Gains (Cooling):

Q_{C,sol} = \sum_{i} (g_{i} \times A_{window,i} \times I_{sol,i} \times F_{shade,i}) \times F_{frame,i}

Thermal Storage Effect:

Q_{C,storage} = Q_{C,peak} \times F_{storage}

Where $F_{storage}$ = Storage factor (0.7-0.9 for heavy construction)

Cooling Load Calculation Method:

Q_{C,N} = \max(0, Q_{C,trans} + Q_{C,vent} + Q_{C,int} + Q_{C,sol} - Q_{C,storage})

Zone-Based Calculation

Zone Heating Demand:

Q_{H,N,zone} = Q_{H,trans,zone} + Q_{H,vent,zone} - Q_{H,int,zone} - Q_{H,sol,zone} - Q_{H,adj,zone}

Where $Q_{H,adj,zone}$ = Heat transfer to adjacent zones

Zone Cooling Demand:

Q_{C,N,zone} = Q_{C,trans,zone} + Q_{C,vent,zone} + Q_{C,int,zone} + Q_{C,sol,zone} - Q_{C,storage,zone} - Q_{C,adj,zone}

Inter-Zone Heat Transfer:

Q_{adj} = H_{adj} \times (\theta_{zone1} - \theta_{zone2}) \times t

Where $H_{adj}$ = Heat transfer coefficient between zones (W/K)

Part 3: Net Energy Demand for Air Conditioning

Sensible Cooling Load

Sensible Cooling Energy:

Q_{C,sensible} = 0.34 \times V_{air} \times (\theta_{e} - \theta_{int}) \times t + Q_{C,trans} + Q_{C,int,sensible} + Q_{C,sol}

Latent Cooling Load

Latent Cooling Energy:

Q_{C,latent} = 0.68 \times V_{air} \times (x_{e} - x_{int}) \times t + Q_{C,int,latent}

Where:

0.68 = Latent heat coefficient (Wh/g·kg)
$x_{e}$ = External absolute humidity (g/kg)
$x_{int}$ = Internal absolute humidity (g/kg)

Moisture Generation Rates:

Source	Moisture Generation (g/h)	Notes
Person (at rest)	40-60	Seated, light activity
Person (active)	100-200	Moderate activity
Cooking	500-2000	Per cooking event
Showering	2000-3000	Per shower
Plants	50-200	Per m² of plants

Dehumidification Energy

Dehumidification Load:

Q_{dehum} = Q_{C,latent} + Q_{dehum,aux}

Where $Q_{dehum,aux}$ = Auxiliary energy for dehumidification

Dehumidification Methods:

Cooling dehumidification
Desiccant dehumidification
Hybrid systems

Humidification Energy

Humidification Load:

Q_{hum} = 0.68 \times V_{air} \times (x_{int} - x_{e}) \times t + Q_{hum,aux}

Where $Q_{hum,aux}$ = Auxiliary energy for humidification

Humidification Methods:

Steam humidification
Evaporative humidification
Ultrasonic humidification

Part 4: Net and Final Energy Demand for Lighting

Daylight Availability

Daylight Factor (DF):

DF = \frac{E_{internal}}{E_{external}} \times 100\%

Where:

$E_{internal}$ = Illuminance at reference point (lux)
$E_{external}$ = External horizontal illuminance (lux)

Typical Daylight Factors:

Room Type	Minimum DF (%)	Average DF (%)
Residential	1-2	2-5
Office	2-3	5-10
Retail	2-4	5-15
Schools	2-3	5-10
Industrial	1-2	2-5

Daylight Utilization Factor:

F_{daylight} = \frac{A_{daylight}}{A_{total}}

Where $A_{daylight}$ = Area with sufficient daylight

Artificial Lighting Demand

Net Lighting Energy Demand:

Q_{L,N} = \sum_{i} (P_{light,i} \times A_{i} \times t_{operation,i} \times (1 - F_{daylight,i}))

Where:

$P_{light,i}$ = Lighting power density (W/m²)
$A_{i}$ = Area (m²)
$t_{operation,i}$ = Operating hours
$F_{daylight,i}$ = Daylight utilization factor

Lighting Power Density:

Space Type	LPD (W/m²)	Notes
Residential	3-6	Standard lighting
Office	8-12	General office
Office (task lighting)	4-8	Task-ambient systems
Retail	15-25	Display lighting
Schools	8-12	Classroom lighting
Corridors	3-6	Circulation spaces

Operating Hours:

Building Type	Annual Operating Hours	Notes
Residential	1000-2000	Varies by occupancy
Office	2000-3000	Business hours
Retail	2500-4000	Extended hours
Schools	1200-1800	School year

Lighting Control Systems

Control System Factors:

Control Type	Energy Reduction Factor	Description
Manual	0.9-1.0	Occupant control
Time switch	0.7-0.9	Scheduled operation
Occupancy sensor	0.5-0.7	Presence detection
Daylight sensor	0.4-0.6	Daylight dimming
Combined (occupancy + daylight)	0.3-0.5	Optimal control

Effective Lighting Energy:

Q_{L,effective} = Q_{L,N} \times F_{control}

Where $F_{control}$ = Control system reduction factor

Final Energy Demand for Lighting

Final Lighting Energy:

Q_{L,F} = \frac{Q_{L,N}}{\eta_{ballast}} + Q_{L,aux}

Where:

$\eta_{ballast}$ = Ballast efficiency (0.85-0.95)
$Q_{L,aux}$ = Auxiliary energy for controls

Part 5: Final Energy Demand of Heating Systems

Boiler Systems

Boiler Efficiency:

\eta_{boiler} = \eta_{nominal} \times F_{load} \times F_{standby}

Where:

$\eta_{nominal}$ = Nominal efficiency
$F_{load}$ = Part-load efficiency factor
$F_{standby}$ = Standby loss factor

Boiler Efficiency Values:

Boiler Type	Nominal Efficiency	Part-Load Factor	Standby Factor
Standard gas boiler	0.88-0.92	0.85-0.95	0.95-0.98
Condensing gas boiler	0.95-0.98	0.90-0.98	0.95-0.98
Standard oil boiler	0.86-0.90	0.85-0.95	0.95-0.98
Condensing oil boiler	0.94-0.97	0.90-0.98	0.95-0.98
Biomass boiler	0.85-0.92	0.80-0.90	0.90-0.95

Final Heating Energy:

Q_{H,F} = \frac{Q_{H,N}}{\eta_{boiler}} + Q_{H,dist} + Q_{H,aux}

Where:

$Q_{H,dist}$ = Distribution losses
$Q_{H,aux}$ = Auxiliary energy (pumps, controls)

Heat Pump Systems

Coefficient of Performance (COP):

COP = \frac{Q_{H,delivered}}{W_{compressor}}

Seasonal Performance Factor (SPF):

SPF = \frac{Q_{H,annual}}{W_{annual}}

SPF Values:

Heat Pump Type	SPF Range	Typical Value
Air source (ASHP)	2.5-3.5	3.0
Ground source (GSHP)	3.5-4.5	4.0
Water source (WSHP)	4.0-5.0	4.5
Exhaust air (EAHP)	2.0-3.0	2.5

Final Heating Energy (Heat Pump):

Q_{H,F} = \frac{Q_{H,N}}{SPF} + Q_{H,aux}

District Heating

District Heating Efficiency:

\eta_{district} = \eta_{production} \times \eta_{distribution}

Typical Values:

Production efficiency: 0.85-0.95
Distribution efficiency: 0.90-0.98
Overall efficiency: 0.77-0.93

Final Heating Energy:

Q_{H,F} = \frac{Q_{H,N}}{\eta_{district}}

Distribution Losses

Distribution Loss Factor:

F_{dist} = 1 + \frac{Q_{dist}}{Q_{H,N}}

Typical Distribution Losses:

System Type	Distribution Loss (%)	Notes
Radiator system	5-10	Standard installation
Underfloor heating	3-7	Low temperature
Fan coil units	8-15	Air handling
District heating	5-15	Varies by network

Distribution Loss Calculation:

Q_{dist} = \sum_{i} (U_{pipe,i} \times L_{pipe,i} \times (\theta_{supply} - \theta_{ambient}) \times t)

Where:

$U_{pipe,i}$ = Pipe heat loss coefficient (W/m·K)
$L_{pipe,i}$ = Pipe length (m)
$\theta_{supply}$ = Supply temperature (°C)
$\theta_{ambient}$ = Ambient temperature (°C)

Storage Losses

Storage Loss Factor:

F_{storage} = 1 + \frac{Q_{storage}}{Q_{H,N}}

Storage Loss Calculation:

Q_{storage} = U_{storage} \times A_{storage} \times (\theta_{storage} - \theta_{ambient}) \times t

Typical Storage Losses:

Storage Type	Loss Factor	Annual Loss (kWh)
Hot water tank (200L)	0.05-0.10	200-500
Buffer tank (500L)	0.03-0.08	300-800
Large storage (1000L+)	0.02-0.05	400-1000

Auxiliary Energy

Auxiliary Energy Components:

Q_{aux} = Q_{pump} + Q_{fan} + Q_{control} + Q_{other}

Pump Energy:

Q_{pump} = \frac{P_{pump} \times t_{operation}}{\eta_{pump}}

Typical Auxiliary Energy:

System Component	Power (W)	Operating Hours	Annual Energy (kWh)
Circulation pump	50-150	2000-4000	100-600
Boiler fan	100-300	1000-2000	100-600
Control system	10-50	8760	90-440

Part 6: Final Energy Demand of Ventilation Systems

Mechanical Ventilation Energy

Fan Energy:

Q_{V,F} = \frac{P_{fan} \times t_{operation}}{\eta_{fan} \times \eta_{motor}}

Where:

$P_{fan}$ = Fan power (W)
$\eta_{fan}$ = Fan efficiency (0.5-0.7)
$\eta_{motor}$ = Motor efficiency (0.8-0.95)

Fan Power Calculation:

P_{fan} = \frac{V_{air} \times \Delta p}{\eta_{fan} \times \eta_{motor} \times 3600}

Where:

$V_{air}$ = Air volume flow (m³/h)
$\Delta p$ = Pressure difference (Pa)

Specific Fan Power (SFP):

SFP = \frac{P_{fan}}{V_{air}}

SFP Requirements:

System Type	Maximum SFP (kW/(m³/s))	Notes
Residential	1.5-2.0	Low pressure systems
Office	1.5-2.5	Standard systems
High-performance	0.8-1.5	Optimized systems

Heat Recovery Systems

Heat Recovery Efficiency:

\eta_{HR} = \frac{\theta_{supply} - \theta_{outdoor}}{\theta_{exhaust} - \theta_{outdoor}}

Typical Heat Recovery Efficiencies:

Heat Recovery Type	Efficiency Range	Typical Value
Plate heat exchanger	0.60-0.75	0.70
Rotary heat exchanger	0.70-0.85	0.80
Run-around coil	0.50-0.70	0.60
Heat pipe	0.40-0.60	0.50

Ventilation Heat Demand with Recovery:

Q_{V,H} = 0.34 \times V_{air} \times (1 - \eta_{HR}) \times (\theta_{int} - \theta_{e}) \times t

Demand-Controlled Ventilation

Ventilation Control Factors:

Control Strategy	Energy Reduction	Notes
Constant volume	0%	Baseline
Time schedule	20-40%	Scheduled operation
CO₂-based	30-50%	Demand-based
Occupancy-based	40-60%	Presence detection
Combined control	50-70%	Multiple sensors

Effective Ventilation Energy:

Q_{V,F,effective} = Q_{V,F} \times F_{control}

Part 7: Final Energy Demand of Air Conditioning Systems

Cooling System Efficiency

Energy Efficiency Ratio (EER):

EER = \frac{Q_{cooling}}{P_{compressor}}

Seasonal Energy Efficiency Ratio (SEER):

SEER = \frac{Q_{cooling,annual}}{P_{annual}}

SEER Values:

System Type	SEER Range	Typical Value
Air-cooled chiller	2.5-4.0	3.0
Water-cooled chiller	4.0-6.0	5.0
Air-source heat pump (cooling)	3.0-4.5	3.5
Ground-source heat pump (cooling)	4.0-6.0	5.0
VRF system	3.5-5.0	4.0

Final Cooling Energy:

Q_{C,F} = \frac{Q_{C,N}}{SEER} + Q_{C,aux}

Heat Rejection Systems

Cooling Tower Energy:

Q_{tower} = P_{tower} \times t_{operation}

Typical Cooling Tower Power:

Tower Type	Power per kW Cooling	Notes
Open cooling tower	0.02-0.05	Water-cooled
Closed cooling tower	0.03-0.06	Indirect cooling
Dry cooler	0.05-0.10	Air-cooled

Dehumidification Energy

Dehumidification Efficiency:

\eta_{dehum} = \frac{Q_{latent}}{Q_{dehum,total}}

Typical Efficiencies:

Cooling dehumidification: 0.3-0.5
Desiccant dehumidification: 0.4-0.6
Hybrid systems: 0.5-0.7

Part 8: Net and Final Energy Demand of Domestic Hot Water

Hot Water Demand

Daily Hot Water Demand:

V_{HW,daily} = n_{persons} \times V_{HW,person}

Per-Person Hot Water Demand:

Building Type	Daily Demand (L/person)	Temperature (°C)
Residential	30-50	60
Hotel	80-120	60
Office	5-10	40-60
Schools	5-15	40-60
Hospitals	100-200	60-80

Annual Hot Water Demand:

V_{HW,annual} = V_{HW,daily} \times 365 \times F_{season}

Where $F_{season}$ = Seasonal variation factor (0.9-1.1)

Net Hot Water Energy Demand

Net Energy Demand:

Q_{W,N} = V_{HW,annual} \times \rho_{water} \times c_{p,water} \times (\theta_{HW} - \theta_{cold})

Where:

$\rho_{water}$ = Water density (1 kg/L)
$c_{p,water}$ = Specific heat (1.16 Wh/kg·K)
$\theta_{HW}$ = Hot water temperature (°C)
$\theta_{cold}$ = Cold water temperature (°C)

Simplified:

Q_{W,N} = V_{HW,annual} \times 1.16 \times (\theta_{HW} - \theta_{cold})

Cold Water Temperature:

Location	Annual Average (°C)	Winter (°C)	Summer (°C)
Northern Germany	8-10	5-7	12-15
Central Germany	10-12	7-9	14-17
Southern Germany	12-14	9-11	16-19

Hot Water System Efficiency

System Efficiency:

\eta_{HW} = \eta_{generation} \times \eta_{distribution} \times \eta_{storage}

Typical Efficiencies:

Component	Efficiency Range	Typical Value
Boiler (gas/oil)	0.85-0.95	0.90
Heat pump	2.5-4.0 (COP)	3.0
Solar thermal	0.40-0.60	0.50
Electric heater	0.95-0.98	0.97
Distribution	0.90-0.98	0.95
Storage	0.85-0.95	0.90

Final Hot Water Energy Demand

Final Energy Demand:

Q_{W,F} = \frac{Q_{W,N}}{\eta_{HW}} + Q_{W,aux}

Distribution Losses:

Q_{W,dist} = U_{pipe} \times L_{pipe} \times (\theta_{HW} - \theta_{ambient}) \times t

Storage Losses:

Q_{W,storage} = U_{storage} \times A_{storage} \times (\theta_{HW} - \theta_{ambient}) \times t

Typical Losses:

System Component	Annual Loss (kWh)	Percentage of Demand
Distribution (standard)	200-500	5-15%
Distribution (insulated)	100-300	3-10%
Storage (200L)	300-600	10-20%
Storage (500L)	500-1000	15-25%

Part 9: Final and Primary Energy Demand of Power Generating Plants

Combined Heat and Power (CHP)

CHP Efficiency:

\eta_{CHP} = \eta_{el} + \eta_{th}

Typical CHP Efficiencies:

CHP Type	Electrical Efficiency	Thermal Efficiency	Total Efficiency
Micro CHP (Stirling)	0.10-0.15	0.75-0.85	0.85-1.00
Small CHP (gas engine)	0.30-0.40	0.50-0.60	0.80-1.00
Medium CHP (gas turbine)	0.25-0.35	0.50-0.60	0.75-0.95
Large CHP	0.35-0.45	0.40-0.50	0.75-0.95

Primary Energy Credit:

Q_{P,credit} = Q_{el,generated} \times f_{P,el,grid} - Q_{fuel} \times f_{P,fuel}

Photovoltaic Systems

PV Energy Generation:

Q_{PV,annual} = A_{PV} \times \eta_{PV} \times I_{solar,annual} \times F_{performance}

Where:

$A_{PV}$ = PV array area (m²)
$\eta_{PV}$ = PV module efficiency (0.15-0.22)
$I_{solar,annual}$ = Annual solar irradiation (kWh/m²)
$F_{performance}$ = Performance ratio (0.75-0.85)

Typical Annual Solar Irradiation:

Location	Annual Irradiation (kWh/m²)	Notes
Northern Germany	900-1000	Lower values
Central Germany	1000-1100	Moderate values
Southern Germany	1100-1200	Higher values

Primary Energy Credit:

Q_{P,PV} = Q_{PV,annual} \times f_{P,el}

Wind Energy Systems

Wind Energy Generation:

Q_{wind,annual} = P_{rated} \times CF \times 8760

Where:

$P_{rated}$ = Rated power (kW)
$CF$ = Capacity factor (0.15-0.35)

Primary Energy Credit:

Q_{P,wind} = Q_{wind,annual} \times f_{P,el}

Energy Storage Systems

Storage Efficiency:

\eta_{storage} = \eta_{charge} \times \eta_{discharge} \times \eta_{self-discharge}

Typical Storage Efficiencies:

Storage Type	Round-Trip Efficiency	Notes
Battery (Li-ion)	0.85-0.95	High efficiency
Battery (lead-acid)	0.70-0.85	Lower efficiency
Thermal storage	0.80-0.90	Seasonal storage
Hydrogen storage	0.40-0.60	Low efficiency

Part 10: Boundary Conditions of Use, Climatic Data

Climate Zones

German Climate Zones:

Zone	Description	Design Temperature Heating (°C)	Design Temperature Cooling (°C)
Zone 1	Very cold	-16 to -12	32-35
Zone 2	Cold	-12 to -8	32-35
Zone 3	Moderate	-8 to -4	32-35
Zone 4	Mild	-4 to 0	32-35
Zone 5	Warm	0 to +4	32-35

Reference Years:

DIN 18599 uses Test Reference Years (TRY) for calculations:

TRY 2010: Standard reference year
TRY 2017: Updated reference year
Location-specific TRY data available

Indoor Design Conditions

Temperature Requirements:

Space Type	Heating Setpoint (°C)	Cooling Setpoint (°C)	Notes
Residential (living)	20	26	Comfort range
Residential (bedroom)	18	26	Lower heating
Office	20	26	Standard office
Retail	20	26	Customer comfort
Schools	20	26	Learning environment
Hospitals	22	24	Higher heating

Humidity Requirements:

Space Type	Relative Humidity (%)	Notes
Residential	30-65	Comfort range
Office	30-65	Standard range
Retail	30-65	Customer comfort
Schools	30-65	Learning environment
Hospitals	40-60	Health requirements

Usage Profiles

Occupancy Profiles:

Building Type	Occupancy Hours	Peak Occupancy	Notes
Residential	16-18 h/day	Evening	Home occupancy
Office	8-10 h/day	Daytime	Business hours
Retail	10-14 h/day	Afternoon	Shopping hours
Schools	6-8 h/day	Morning	School hours

Internal Heat Gain Profiles:

Time	Residential	Office	Retail
0-6	Low	Very low	Very low
6-8	Medium	Low	Low
8-12	Low	High	Medium
12-14	Medium	Medium	High
14-18	Low	High	High
18-22	High	Low	Medium
22-24	Medium	Very low	Low

Part 11: Building Automation

Control System Efficiency

Control Efficiency Factor:

F_{control} = \frac{Q_{with,control}}{Q_{without,control}}

Typical Control Efficiencies:

Control Type	Energy Reduction	Notes
Manual control	0%	Baseline
Time schedule	10-20%	Scheduled operation
Temperature control	15-25%	Setpoint control
Demand-based	20-40%	Sensor-based
Predictive control	25-45%	Advanced algorithms
Integrated BMS	30-50%	Comprehensive control

Building Management Systems (BMS)

BMS Functions:

Heating/cooling control
Ventilation control
Lighting control
Shading control
Energy monitoring
Fault detection

BMS Energy Impact:

Q_{BMS,savings} = Q_{baseline} \times F_{BMS}

Where $F_{BMS}$ = BMS efficiency factor (0.5-0.7)

Demand-Based Control

Occupancy-Based Control:

F_{occupancy} = 1 - \frac{t_{unoccupied}}{t_{total}}

Time-Based Control:

F_{time} = \frac{t_{operation}}{t_{total}}

Combined Control:

F_{combined} = F_{occupancy} \times F_{time} \times F_{demand}

Part 12: Tabulation Method for Residential Buildings

Simplified Calculation Method

Tabulated U-Values:

Building Element	U-Value (W/m²·K)	Notes
External wall (standard)	0.24-0.35	EnEV minimum
External wall (improved)	0.15-0.24	Better insulation
Roof (standard)	0.20-0.30	EnEV minimum
Roof (improved)	0.12-0.20	Better insulation
Ground floor (standard)	0.30-0.40	EnEV minimum
Ground floor (improved)	0.20-0.30	Better insulation
Window (standard)	1.3-1.8	Double glazing
Window (improved)	0.8-1.3	Triple glazing

Tabulated Heat Loss Coefficients:

Building Type	H_{trans} (W/K per m² floor)	Notes
Detached house	0.4-0.6	Single family
Semi-detached	0.3-0.5	Shared wall
Terraced house	0.25-0.4	Multiple shared walls
Apartment (mid)	0.2-0.35	Internal unit
Apartment (top)	0.25-0.4	Top floor

Quick Assessment Tables

Energy Performance Classes:

Class	EPI Range (kWh/m²·a)	Description
A+	< 30	Very high efficiency
A	30-50	High efficiency
B	50-75	Good efficiency
C	75-100	Standard efficiency
D	100-130	Below standard
E	130-160	Poor efficiency
F	160-200	Very poor efficiency
G	200-250	Extremely poor
H	> 250	Worst efficiency

Part 13: Detailed Load Calculations

Internal Temperature Calculation

Steady-State Temperature:

\theta_{int} = \theta_{e} + \frac{Q_{int} + Q_{sol}}{H_{total}}

Where $H_{total}$ = Total heat loss coefficient (W/K)

Sensible Heat Loads

Sensible Cooling Load:

Q_{C,sensible} = H_{total} \times (\theta_{e} - \theta_{int}) + Q_{int,sensible} + Q_{sol}

Sensible Heating Load:

Q_{H,sensible} = H_{total} \times (\theta_{int} - \theta_{e}) - Q_{int,sensible} - Q_{sol}

Latent Heat Loads

Latent Cooling Load:

Q_{C,latent} = 0.68 \times V_{air} \times (x_{e} - x_{int}) + Q_{int,latent}

Latent Heating Load:

Q_{H,latent} = 0.68 \times V_{air} \times (x_{int} - x_{e}) - Q_{int,latent}

Comprehensive Calculation Example

Building Description

Building:

Residential building, 150 m² net floor area
Location: Central Germany (Climate Zone 3)
Construction: 2010, standard insulation
Heating: Condensing gas boiler
Ventilation: Mechanical ventilation with heat recovery
Hot water: Integrated with heating system
Windows: Double-pane Low-E glazing

Step 1: Building Characteristics

U-Values:

External walls: 0.28 W/m²·K
Roof: 0.22 W/m²·K
Ground floor: 0.35 W/m²·K
Windows: 1.4 W/m²·K (U-value), g-value = 0.60

Areas:

External walls: 120 m²
Roof: 75 m²
Ground floor: 75 m²
Windows: 25 m² (south: 10 m², east: 8 m², west: 7 m²)

Step 2: Net Heating Energy Demand

Transmission Losses:

H_{trans} = 120 \times 0.28 + 75 \times 0.22 + 75 \times 0.35 + 25 \times 1.4 = 33.6 + 16.5 + 26.25 + 35 = 111.35 \text{ W/K}

Ventilation Losses: Air change rate: $n = 0.5$ 1/h Room volume: $V = 150 \times 2.5 = 375$ m³

H_{vent} = 0.34 \times 0.5 \times 375 = 63.75 \text{ W/K}

Total Heat Loss Coefficient:

H_{total} = 111.35 + 63.75 = 175.1 \text{ W/K}

Heating Degree Days: For Central Germany: HDD = 3500 K·d

Transmission Energy:

Q_{H,trans} = 111.35 \times 3500 \times 24 / 1000 = 9,353 \text{ kWh/a}

Ventilation Energy:

Q_{H,vent} = 63.75 \times 3500 \times 24 / 1000 = 5,355 \text{ kWh/a}

Internal Gains:

Q_{H,int} = 150 \times 4 \times 2000 / 1000 = 1,200 \text{ kWh/a}

Solar Gains: South windows: $10 \times 0.60 \times 600 = 3,600$ kWh/a East windows: $8 \times 0.60 \times 400 = 1,920$ kWh/a West windows: $7 \times 0.60 \times 400 = 1,680$ kWh/a

Q_{H,sol} = 3,600 + 1,920 + 1,680 = 7,200 \text{ kWh/a}

Net Heating Energy:

Q_{H,N} = 9,353 + 5,355 - 1,200 - 7,200 = 6,308 \text{ kWh/a}

Step 3: Final Heating Energy Demand

Boiler Efficiency: Condensing gas boiler: $\eta_{boiler} = 0.96$

Distribution Losses:

F_{dist} = 1.08

(8% losses)

Storage Losses:

F_{storage} = 1.05

(5% losses)

Auxiliary Energy:

Q_{aux} = 300 \text{ kWh/a}

Final Heating Energy:

Q_{H,F} = \frac{6,308}{0.96} \times 1.08 \times 1.05 + 300 = 7,751 \text{ kWh/a}

Step 4: Hot Water Energy Demand

Daily Demand: 4 persons × 40 L/person = 160 L/day

Annual Demand:

V_{HW,annual} = 160 \times 365 = 58,400 \text{ L/a}

Net Energy:

Q_{W,N} = 58,400 \times 1.16 \times (60 - 10) / 1000 = 3,387 \text{ kWh/a}

Final Energy:

Q_{W,F} = \frac{3,387}{0.96} \times 1.08 \times 1.05 + 100 = 4,110 \text{ kWh/a}

Step 5: Ventilation Energy

Fan Power:

V_{air} = 0.5 \times 375 = 187.5 \text{ m³/h}

P_{fan} = 187.5 \times 200 / (0.6 \times 0.9 \times 3600) = 19.3 \text{ W}

Annual Fan Energy:

Q_{V,F} = 19.3 \times 8760 / 1000 = 169 \text{ kWh/a}

Heat Recovery Savings:

\eta_{HR} = 0.75

Q_{V,savings} = 0.34 \times 187.5 \times 0.75 \times 3500 \times 24 / 1000 = 4,016 \text{ kWh/a}

Step 6: Primary Energy Demand

Heating Primary Energy:

Q_{P,H} = 7,751 \times 1.1 = 8,526 \text{ kWh/a}

Hot Water Primary Energy:

Q_{P,W} = 4,110 \times 1.1 = 4,521 \text{ kWh/a}

Ventilation Primary Energy:

Q_{P,V} = 169 \times 1.8 = 304 \text{ kWh/a}

Total Primary Energy:

Q_{P,total} = 8,526 + 4,521 + 304 = 13,351 \text{ kWh/a}

Energy Performance Indicator:

EPI = \frac{13,351}{150} = 89.0 \text{ kWh/m²·a}

Energy Performance Class: C (75-100 kWh/m²·a)

Best Practices and Design Guidelines

Design Optimization Strategies

Building Envelope:

Optimize U-values based on cost-benefit analysis
Minimize thermal bridges
Optimize window-to-wall ratio
Select appropriate glazing for orientation

Heating Systems:

Use high-efficiency condensing boilers
Consider heat pumps for low-temperature systems
Optimize distribution systems
Implement proper controls

Ventilation:

Use heat recovery systems
Implement demand-controlled ventilation
Optimize fan efficiency (low SFP)
Consider natural ventilation where appropriate

Lighting:

Maximize daylight utilization
Use efficient lighting technologies (LED)
Implement automatic controls
Consider task-ambient lighting

Calculation Accuracy

Input Data Quality:

Use verified material properties
Accurate building geometry
Correct climate data
Realistic usage profiles

System Modeling:

Account for all energy systems
Include distribution losses
Consider auxiliary energy
Model control systems accurately

Validation:

Compare to similar buildings
Check against benchmarks
Verify with measurements
Review for reasonableness

Common Calculation Errors

Underestimating Losses:

Error: Ignoring distribution losses
Impact: 5-15% underestimation
Solution: Include all loss components

Incorrect Primary Energy Factors:

Error: Using outdated factors
Impact: Significant errors in primary energy
Solution: Use current official factors

Simplified Assumptions:

Error: Over-simplifying usage profiles
Impact: 10-30% error
Solution: Use detailed profiles

Missing Components:

Error: Ignoring auxiliary energy
Impact: 5-10% underestimation
Solution: Include all energy components

Software Tools and Implementation

DIN 18599 Calculation Software

Commercial Software:

EnEV-Planer
ArchiPHYSIK
PHPP (Passive House Planning Package)
Hottgenroth Software
EnEV-Online

Features:

Complete DIN 18599 implementation
Building modeling
System selection
Report generation
Energy Performance Certificate generation

Calculation Workflow

Step 1: Building Input

Geometry and areas
Construction details
U-values and thermal bridges
Window properties

Step 2: System Definition

Heating system
Cooling system
Ventilation system
Hot water system
Lighting system

Step 3: Usage Definition

Occupancy profiles
Operating schedules
Internal gains
Climate data

Step 4: Calculation

Net energy demand
Final energy demand
Primary energy demand
Energy Performance Indicator

Step 5: Reporting

Energy Performance Certificate
Detailed calculation report
Compliance verification
Optimization recommendations

Regulatory Compliance

German Energy Saving Ordinance (EnEV)

Requirements:

Maximum primary energy demand
Minimum thermal insulation
Maximum transmission heat loss
Energy Performance Certificate

Compliance Verification:

Calculation according to DIN 18599
Verification of all requirements
Documentation and reporting
Building permit approval

Building Energy Act (GEG)

Current Requirements (2024):

Primary energy demand limits by building type
Renewable energy requirements
Building Energy Certificate
Regular updates and tightening

Future Requirements:

Increasingly strict limits
Higher renewable energy shares
Life-cycle assessment
Digital building logbook

Conclusion

DIN 18599 provides a comprehensive framework for calculating building energy performance, covering all aspects from net energy demand through final energy to primary energy. This standard is essential for:

Regulatory Compliance:

Meeting German building energy regulations
Obtaining building permits
Generating Energy Performance Certificates
Demonstrating code compliance

Design Optimization:

Comparing design alternatives
Identifying energy efficiency measures
Optimizing system selection
Cost-benefit analysis

Performance Assessment:

Verifying design performance
Post-construction evaluation
Building energy rating
Benchmarking and comparison

Key Principles:

Comprehensive energy balance
Zone-based calculations
System efficiency accounting
Primary energy evaluation
Monthly balance methodology

Critical Factors:

Accurate input data
Complete system modeling
Proper climate data
Realistic usage profiles
Current primary energy factors

Best Practices:

Use verified calculation software
Include all energy components
Account for system losses
Consider auxiliary energy
Validate results

By applying DIN 18599 methodologies correctly, engineers and designers can accurately assess building energy performance, optimize designs, ensure regulatory compliance, and contribute to improved building energy efficiency. The standard's comprehensive approach ensures that all aspects of building energy use are properly evaluated, from the building envelope through all energy systems to the final primary energy demand.

The complexity of DIN 18599 reflects the complexity of building energy systems, but mastering this standard enables accurate energy performance assessment and effective energy efficiency optimization. As building energy regulations continue to tighten and the focus on sustainability increases, understanding and applying DIN 18599 becomes increasingly important for building professionals.

For specific projects and detailed calculations, consult with experienced energy consultants and use validated calculation software. Continuous learning and staying current with standard updates and regulatory changes ensures accurate and compliant energy performance assessments.